Is the measurement of SvO2 a reliable indicator of oxygenation on VV-ECMO?
Because of recirculation, measuring SvO2 is not a reliable indicator of oxygenation on VV-ECMO. However, it is a useful indicator for VA-ECMO and should be maintained at 65-75%.
In VV-ECMO, blood is drained from the venous system, oxygenated outside the body, and then returned to the venous system. A common issue with this configuration is recirculation, where some of the oxygenated blood re-enters the ECMO circuit without passing through the systemic circulation. This phenomenon leads to inaccurately high SvO2 readings, which do not reflect the patient's oxygenation status. See my past Newsletter article "Understanding and Managing Recirculation in VV ECMO" for more in-depth information about recirculation.
In contrast, VA-ECMO provides direct arterial blood flow, bypassing the heart and lungs. The measurement of SvO2 in VA-ECMO is more reliable because it accurately reflects the balance between oxygen delivery and consumption in the systemic circulation. Maintaining SvO2 within the target range of 65-75% in VA-ECMO ensures adequate tissue oxygenation and helps guide adjustments in ECMO flow, ventilator settings, and other supportive measures.
Thus, while SvO2 is a valuable monitoring parameter in VA-ECMO, the ECMO Specialist should use alternative indicators such as lactate levels, urine output, peripheral perfusion, and Near-Infrared Spectroscopy (NIRS) to assess oxygenation in patients on VV-ECMO. Optimizing oxygen delivery in VV-ECMO involves carefully managing cannula placement, pump flow, and hemoglobin levels to minimize recirculation and enhance overall patient care.
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Acknowledgments:
I developed three custom GPTs, “AI ECMO Expert,” “ECMO Specialist Handover Practice,” and “Micro Definitions (MD-GPT),” for specialized research. These tools draw primarily from the ELSO Redbook (6th Edition), the ELSO Specialist Training Manual (4th Edition), various research papers, and articles. Additional research was supported by GPT-4o/o1, Claude 3.5 Sonnet/Opus, and Perplexity. Editing was performed with Grammarly. A.I. images and charts were created using Leonardo AI, DALL-E3 AI Image Generator, Microsoft Designer, and Adobe Express. Content for all articles sourced from Extracorporeal Life Support: The ELSO Red Book, 6th Edition, and ECMO Specialist Training Manual, 4th Edition.